The invention concerns a substrate with a structured surface and methods for the production of the substrate with a structured surface and also methods for determining the wetting properties of that substrate. The method according to the invention can be used to produce in particular substrates with user-specific fixed surface properties—implants are named by way of example—. Thus implants like for example dental implants or endoprotheses which are distinguished by particularly good ingrowth at the implantation location in the jaw or extremity bones can thus be produced with the method according to the invention.
In recent years it has become increasingly clear that the roughness of the surface of an implant, besides hydrophilicity and hydrophobicity of the implant surface, plays one of the most important parts in the integration of implants. Roughness can increase by hydrophilicity and also hydrophobicity. Thus it is known in the state of the art that an SLA (sand-blasted acid etched) surface exhibits a substantially better ingrowth behaviour than the smooth machined form of titanium. Besides the SLA surface with a roughness there are implants with a TPS (titanium plasma sprayed) surface, which exhibits a roughness with a better integration healing behaviour.
The presence of a rough surface is always linked to an increase in surface area in comparison with a smooth surface. Thus for example the SLA and TPS surfaces, in comparison with a smooth surface, can have a surface area which is 2-20 times greater, and that has a positive effect in particular in the case of ingrowth in animals and humans.
A disadvantage of rough surfaces is the problem of removal in the event of implant revisions. What is common in particular to the previously produced implants is that the outwardly facing surfaces of the object generally have irregular structures which adversely affect the ingrowth behaviour in particular for use of the objects as implants, and do not positively influence same. In addition titanium particles can become detached from the TPS surface and pass into the tissue.
Added to that is a reproduction capability, which needs to be improved, of the implants produced in that way as implants produced both using the SLA method and also using the TPS method exhibit a certain statistical breadth in respect of the surface properties and it is therefore necessary to observe with the utmost accuracy the method parameters in dependence on the starting material for the purposes of standardising the implants.
Consideration was given on the part of the inventor to improving the surface properties and it was discovered that an optimally structured of the implant can be afforded with a microstructure. It was demonstrated by the inventor that reverse engineering leads to a surface with properties which are improved in relation to the two above-mentioned SLA and TPS surfaces, wherein the improved surfaces can be produced with a lower risk potential.
It was further discovered on the part of the inventor that such rough implant surfaces can be made further hyperhydrophilic, as is described hereinafter, by means of wet-chemical methods and/or by functionalisation with hydrophilic organic molecules.
It will be noted however that the production of such hyperhydrophilic surfaces generally requires the use of highly heated acids and the corresponding plasma chambers. In relation to those hyperhydrophilic surfaces hitherto the dynamic contact angles were measured with ultrapure water in the form of the advancing angle (θV) and the receding angle (θR) in accordance with the observations of the inventor with the value zero (θV/θR=0°/0°). In reality the contact angles are in the imaginary range.